In a sterilization apparatus using an electron beam, when the electron beam is irradiated onto a work piece to be sterilized, nitrogen oxide is generated. The nitrogen oxide is then dissolved, in an atmosphere having a water content, into water, and changes into nitric acid. Since the nitric acid has a corrosive nature, the life time of a sterilization apparatus becomes lowered. In order to use the sterilization apparatus using the electron beam for a long term, it is necessary to periodically change parts and the like of the sterilization apparatus, resulting in an increase in the running cost. In addition, the use of a specific work piece having a strength against corrosion also results in a cost increasing, thus providing a problem.
Then, there has already been proposed an electron beam irradiation apparatus for preventing the generation of nitrogen oxide by supplying a dried gas into an electron beam irradiation chamber (refer to Patent Publication 1: Japanese Patent Application Laid-open Publication No. 9-222500).
The invention disclosed in the above Patent Publication 1 is an electron beam irradiation apparatus which irradiates a work piece to be treated with the electron beam, which is being conveyed within an irradiation chamber by a conveying means such as a conveyer or the like, and in order to reduce the water content in an atmosphere in the irradiation chamber, gas passing through a drying apparatus is supplied into the irradiation chamber.    Patent Publication 1: Japanese Patent Application Laid-open Publication No. 9-222500